Bare-stem plants - Psilopsida

Japanese: 裸茎植物 - らけいしょくぶつ（英語表記）Psilopsida

When vascular plants are divided into four lineages based mainly on the nature of their leaves, the group of plants that do not differentiate into leaves or roots is called the naked-stem plants (psilophytes), also known as psilophytes. Extant species are classified into two genera, Psilophytes and Psilophytes, and are treated as independent families, but no fossils are known, and they are considered to have no direct phylogenetic relationship with the archaic Psilophytes that became extinct in the Devonian period. Archaic Psilophytes were thought to be a single lineage without leaves or roots, but it has been revealed that they are divided into three groups: the Rhynia group, which has no appendages on the surface of the stem, bifurcated stems, and apical sporangia; the Trimerophyton group, which occasionally has appendages on the surface of the stem, may branch into three or more branches, and has apical but often recurved sporangia; and the Zosterophyllum group, which has leaf-like appendages on the surface of the stem, uniaxially branched stems, and axial sporangia.

Source: Heibonsha World Encyclopedia, 2nd Edition Information

Japanese:

維管束植物を主として葉の性質で四つの系統に区分した場合，葉も根も分化しない植物群を裸茎植物(英名psilophytes)といい，マツバラン類などともいう。現生種はマツバラン属とイヌナンカクラン属の2属に分類され，それぞれ独立の科として扱われるが，化石は知られておらず，デボン紀に滅んでしまった古生マツバラン類とは直接の系統関係はないとみなされている。古生マツバラン類は，葉も根もない一つの系統群と考えられていたが，茎の表面に付属物をつけず，茎が二叉（にさ）分枝し，胞子囊を頂生するライニア群，茎の表面に付属物をまれにつけ，茎は三叉以上に分枝することがあり，胞子囊は頂生するがしばしば反曲するトリメロフィトン群，茎の表面に葉的付属物をつけ，茎は単軸分岐し，胞子囊は軸生のゾステロフィルム群の3群に分かれることが明らかとなっている。

出典　株式会社平凡社世界大百科事典第２版について　情報

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